1. Field of the Invention
The present invention pertains to a connecting rod assembly for use in an internal combustion engine. This connecting rod is suitable for high volume assembly with automated equipment.
2. Disclosure Information
The connecting rod has an important role in a reciprocating internal combustion engine the attaching of the pistons to the crankshaft. Criticalities exist with respect to connecting rods. A first criticality is that the joint between the connecting rod and crankshaft must be carefully built so as to assure that the engine has a long service life and is quiet in operation. The desire for quietness, as well as fuel economy resulting from appropriately low dynamic friction, has led engine manufacturers to use connecting rods with caps that are formed integrally from the parent metal of the connecting rod and then removed by cracking the cap from the balance of the connecting rod. Techniques for manufacturing such cracked rods, as they are termed in automotive parlance, are beyond the scope of this specification.
A second criticality or problem with cracked rods resides in the fact that connecting rod caps may sometime be easily fit to the beam portion of the connecting rod in either of two orientations. Unfortunately, only one orientation is correct because the micro structure created when the cap is cracked from the beam portion of the connecting rod prevents the cap from being positioned so as to achieve the correct circularity of the connecting rod""s crankshaft journal bore. As a result, engine durability and noise considerations may be adversely affected. The fact is that conventional rod cracking techniques frequently result in components in which it is very difficult, without the aid of magnification instruments, to determine the proper orientation of the connecting rod cap with respect to the beam portion of the rod.
A connecting rod according to the present invention prevents the problem of misoriented connecting rod caps by providing a connecting rod structure which will allow the machine screws which extend through the cap to be installed if and only if the cap is in the proper orientation vis-à-vis the beam portion of the connecting rod.
A connecting rod assembly for a reciprocating internal combustion engine includes a beam portion having a first end for receiving a wrist pin attached to a piston and a second end for engaging a crankshaft journal. A cap for maintaining the second end of the beam portion in contact with a crankshaft is joined to the second end of the beam portion along a parting plane. At least one fastener maintains the cap in contact with the second end of the beam portion. The fastener is mounted or received within a bore extending through the cap as well as substantially through the second end of the beam portion. The bore through which the fastener extends has a central axis which is not normal or perpendicular to the parting plane extending between the cap and the beam portion of the connecting rod. The beam portion and the cap are preferably manufactured as a unit from which the cap is fractured after the larger, or the bottom end, of the connecting rod has been honed and otherwise finished.
The plurality of fasteners extending through the cap is preferably threadedly engaged with the second end of the beam portion to maintain the cap in contact with the beam portion.
Each of the fasteners used to maintain the cap in contact with the second end of the beam portion has a central axis which is preferably parallel to the central axis of the other fasteners used to mount the cap to the beam portion of the connecting rod. In any event, none of the bores extending through the cap and the beam portion of the connecting rod is perpendicular to the parting plane defined by the intersection of the cap and the second end of the beam portion, with the result that fasteners may be run down into the beam portion of the connecting rod only if the cap is installed in the proper orientation.
It is an advantage of the present invention that a connecting rod made according to this invention will be highly resistant to misbuilding i.e. attachment of the cap in an improper orientation.
It is an advantage of the present invention that use of a connecting rod according to this invention will obviate the need for inspections based on the possibility that a cap may be incorrectly installed upon the beam portion of the connecting rod.
It is a further advantage of the present invention that connecting rods built according to this invention will be easily maintained in the field, because the proper orientation of the cap with respect to the remainder of the rod will be assured.
It is yet another advantage of the present invention that connecting rods build according to this invention will provide an anti-misbuild feature at little, if any, additional manufacturing cost.
Other advantages, as well as features and objects of the present invention will become apparent to the reader of this specification.